Integrated circuit including back side conductive lines for clock signals

ABSTRACT

An integrated circuit is disclosed, including a first latch circuit, a second latch circuit, and a clock circuit. The first latch circuit transmits multiple data signals to the second latch circuit through multiple first conductive lines disposed on a front side of the integrated circuit. The clock circuit transmits a first clock signal and a second clock signal to the first latch circuit and the second latch circuit through multiple second conductive lines disposed on a backside, opposite of the front side, of the integrated circuit.

CROSS-REFERENCE

The present application claims priority to U.S. Provisional PatentApplication No. 63/017,905, filed on Apr. 30, 2020, which isincorporated by reference herein in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1A is a top view diagram of part of an integrated circuit,according to some embodiments of the present disclosure.

FIG. 1B is a sectional view diagram illustrating a structure of somecell rows along a sectional line in FIG. 1A, according to someembodiments of the present disclosure.

FIG. 2A is a schematic diagram of an integrated circuit, according tosome embodiments of the present disclosure.

FIG. 2B is a detailed circuit of the scan flip flop circuit of FIG. 2A,according to some embodiments of the present disclosure.

FIGS. 3A-3B illustrate layout diagrams in a plan view of part of a frontside of the scan flip flop circuit in FIG. 2B, according to someembodiments of the present disclosure.

FIG. 3C illustrates layout diagram and cross-section views of part of aback side of the scan flip flop circuit in FIG. 2B, according to someembodiments of the present disclosure.

FIG. 4 is a layout diagram in a plan view of part of an integratedcircuit, in accordance with various embodiments.

FIG. 5 illustrates layout diagram and cross-section views of part of anintegrated circuit, in accordance with various embodiments.

FIG. 6 is a flow chart of a method of manufacturing an integratedcircuit, in accordance with some embodiments of the present disclosure.

FIG. 7 is a block diagram of a system for designing the integratedcircuit layout design, in accordance with some embodiments of thepresent disclosure.

FIG. 8 is a block diagram of an integrated circuit manufacturing system,and an integrated circuit manufacturing flow associated therewith, inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The terms used in this specification generally have their ordinarymeanings in the art and in the specific context where each term is used.The use of examples in this specification, including examples of anyterms discussed herein, is illustrative only, and in no way limits thescope and meaning of the disclosure or of any exemplified term.Likewise, the present disclosure is not limited to various embodimentsgiven in this specification.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Reference is now made to FIG. 1A. FIG. 1A is a top view diagram of partof an integrated circuit 10, in accordance with some embodiments. Asillustratively shown in FIG. 1A, the integrated circuit 10 includesseveral cell rows ROW1-ROW4. In some embodiments, there are cells, forexample, cells illustrated in FIGS. 3A-3C, and 4-5, are implemented byintegrated circuits arranged in these cell rows ROW1-ROW4. The number ofthe cell rows ROW1-ROW4 in the integrated circuit 10 in FIG. 1A is givenfor illustrative purposes. Various numbers of the cell rows ROW1-ROW4are within the contemplated scope of the present disclosure. Forexample, in some embodiments, the number of the cell rows in theintegrated circuit 10 is more than 4.

For illustration, the cell rows ROW1-ROW4 extend along x direction andare parallel to each other. In some embodiments, the cell rows ROW1-ROW4are arranged along y direction, which is substantially perpendicular tothe x direction.

In some embodiments, there are two groups of cell rows among the rowsROW1-ROW4 in reference with their row heights. As illustratively shownin FIG. 1A, each of the cell rows ROW1 and ROW3 is configured to have arow height H1, and each of the cell rows ROW2 and ROW4 is configured tohave another row height H2, which is shorter than the row height H1. Thecell rows ROW1 and ROW3 with the row height H1 are regarded as a firstgroup “A” of the cell rows ROW1-ROW4, and the cell rows ROW2 and ROW4are regarded as a second group “B” of the cell rows ROW1-ROW4. In someembodiments, as depicted in FIG. 1A, the first group A of the cell rowsand the second group B of the cell rows are interlaced.

For illustration, the cell row ROW1 with the row height H1 in the firstgroup “A” includes two active areas 110-120, and the cell row ROW2 withthe row height H2 in the second group “B” includes two active areas130-140. Similarly, the cell row ROW3 includes two active areas 150-160,and the cell row ROW4 includes two active areas 170-180. Forillustration, the active areas 110-180 extend along x direction and areseparate from each other in y direction. The configurations of theactive areas 110-180 will be discussed in the following paragraphs withFIG. 1B.

In some embodiments, the active areas 120 and 140 have a conductivity ofP type, while the active areas 110 and 130 have a conductivity of Ntype. The configurations of the active areas 150 and 180 are similar tothe active areas 110 and 140, and the configurations of the active areas160 and 170 are similar to the active areas 120 and 130. Alternativelystated, the cell rows ROW1-ROW4 are interlaced in a periodic sequencealong y direction. The configurations of the active areas 110-180 aregiven for illustrative purposes. Various implements of the active areas110-180 are included in the contemplated scope of the presentdisclosure. For example, in some embodiments, the active areas 110, 140,150, and 180 are N type and the active areas 120, 130, 160 and 170 are Ptype.

The configurations of the integrated circuit 10 of FIG. 1A are given forillustrative purposes. Various implements of the integrated circuit 10are includes in the contemplated scope of the present disclosure. Forexample, in some embodiments discussed in the following paragraphs, thecell rows are arranged in sequence different from the cell rows ROW1 toROW4, such like, in sequence ROW1, ROW2, ROW4, and ROW3. Alternativelystated, the cell rows having the same height are arranged abutted eachother.

Reference is now made to FIG. 1B. FIG. 1B is a sectional view diagramillustrating a structure of the cell rows ROW3-ROW4 along a sectionalline AA′ in FIG. 1A in accordance with some embodiments. With respect tothe embodiments of FIG. 1A, like elements in FIG. 1B are designated withthe same reference numbers for ease of understanding.

As illustratively shown in FIG. 1B, the cell row ROW1 with the rowheight H1 in the second group “A” includes two active areas 110-120 onthe substrate Sub. The active area 110 of the cell row ROW1 includes afirst one fin-shaped structure, and the active area 120 of the cell rowROW1 includes a second one fin-shaped structure. Alternatively stated,each one of the active areas 110-120 includes one fin-shaped structure.

As illustratively shown in FIG. 1B, the cell row ROW2 with the rowheight H1 in the first group “B” includes the active areas 130-140 on asubstrate Sub. The active area 130 of the cell row ROW2 includes twofin-shaped structures 131 and 132, and the active area 140 of the cellrow ROW2 includes another two fin-shaped structures 141 and 142.Alternatively stated, each one of the active areas 130-140 include twofin-shaped structures, such as 131 and 132, or 141 and 142.

In some embodiments, the fin-shaped structures 131 and 132 are n-typefin-shaped structures, and the fin-shaped structures 141 and 142 arep-type fin-shaped structures. In some other embodiments, the fin-shapedstructures 131 and 132 are p-type fin-shaped structures, and thefin-shaped structures 141 and 142 are n-type fin-shaped structures.

The fins mentioned above may be patterned by any suitable method. Forexample, the fins may be patterned using one or more photolithographyprocesses, including double-patterning or multi-patterning processes.Generally, double-patterning or multi-patterning processes combinephotolithography and self-aligned processes, allowing patterns to becreated that have, for example, pitches smaller than what is otherwiseobtainable using a single, direct photolithography process. For example,in one embodiment, a sacrificial layer is formed over a substrate andpatterned using a photolithography process. Spacers are formed alongsidethe patterned sacrificial layer using a self-aligned process. Thesacrificial layer is then removed, and the remaining spacers may then beused to pattern the fins.

In some embodiments, such an active area may include one or morefin-shaped structures of one or more three-dimensionalfield-effect-transistors (e.g., FinFETs, gate-all-around (GAA)transistors), or an oxide-definition (OD) region of one or more planarmetal-oxide-semiconductor field-effect transistors (MOSFETs). The activeregion may serve as a source feature or a drain feature of therespective transistor (s).

In some embodiments, the active area 130 of the cell row ROW2 includestwo fin-shaped structures 131 and 132 together as an active region toform an integrated circuit component (such as a transistor), such thatan equivalent width of the active region of the integrated circuitcomponent disposed on the active area 130 will be wider than one ofanother integrated circuit component disposed on the active area 110,which includes the first one fin-shaped structure. Alternatively stated,in some embodiments, integrated circuit components disposed on the cellrow ROW2 have a better performance, for example, faster computing speed,than integrated circuit components disposed on the cell row ROW1.

Reference is now made to FIG. 2A. FIG. 2A is a schematic diagram of anintegrated circuit, according to some embodiments of the presentdisclosure. In some embodiments, the integrated circuit includes a scanflip-flop circuit 200 formed in the integrated circuit 10 of FIG. 1A.For illustration, the scan flip-flop circuit 200 includes a scanmultiplexer 210 and a flip-flop circuit 220. In some embodiments, thescan multiplexer 210 includes a scan mux input circuit 211 and a scanenable inverter 212. The flip-flop circuit 220 includes a master latchcircuit 221, a slave latch circuit 222, a data out circuit 223, and aclock circuit 224 including clock inverters 224 a and 224 b.

In some embodiments, the scan mux input circuit 211 receives a scan datainput SI (i.e., a test vector signal, such used in Built-In-Self-Test(BIST) scanning or boundary test scanning), normal data input D (i.e.,actual application data rather than test data), a scan enable signal SE,and a scan enable bar signal SEB transmitted from the scan enableinverter 212. In operation, the scan enable signal SE governs whetherthe scan data input SI or the normal data input D is selected. Forexample, if the scan enable signal SE is enabled (e.g., set to a logical“1”), the scan multiplexer 210 outputs the scan data input SI as aselected data SD. On the other hand, if the scan enable signal SE isdisabled (e.g., set to a logical “0”), the scan multiplexer 210 outputsnormal data input D as the selected data SD.

In some embodiments, the master latch circuit 221 and the slave latchcircuit 222 are cross-coupled to store a data state in mutuallyreinforcing fashion, and each receives clock signals clkb and clk. Invarious embodiments, a signal mq_x is transmitted between the masterlatch circuit 221 and the slave latch circuit 222. The data out circuit223 has an input coupled to an output of the slave latch circuit 222 toreceive a signal of and outputs the data out signal Q. The clock signalsclkb and clk are based on a clock signal CP and are provided by theclock circuit 224. The clock inverter 224 a inverts the clock signal CPand outputs the clock signal clkb, and the clock inverter 224 b invertsthe clock signal clkb and output the clock signal clk. Accordingly, theclock signals clk and clkb are out-of-phase.

In operation, the flip-flop circuit 220 receives the selected data SDand generates an output data signal Q. The output data signal Q is basedon the present state stored in the flip-flop circuit 220, the selecteddata SD, and the clock signal CP. The output data signal Q “flips” and“flops” between a “1” state and a “0” state in a manner that depends onthe selected data SD and the clock signal CP. In some embodiments, theflip-flop circuit 220 continues to output its currently stored state asoutput data signal Q until the clock signal CP exhibits a rising and/orfalling edge (regardless of changes in the selected data SD). When theclock signal CP exhibits a rising and/or falling edge, only then theflip-flop circuit 220 “stores” the present state of the selected signalSD and delivers this state as the output data signal Q.

Reference is now made to FIG. 2B. FIG. 2B is a detailed circuit of thescan flip flop circuit 200 of FIG. 2A, according to some embodiments ofthe present disclosure. As shown in FIG. 2B, the scan flip flop circuit200 includes P-type transistors P1-P5, P7-P13, P15-P18, P20 and N-typetransistors N1-N5, N7-N13, N15-N18, N20.

Specifically, the transistors P1-P4, P11, N1-N4, and N11 are operablycoupled to form the scan multiplexer 210 while the transistors P11-N11are configured to form the scan enable inverter 212. The master latchcircuit 221 includes the transistors P7, N7 establish an invertercoupled to the scan multiplexer 210, and further includes thetransistors P8-P9, N8-N9 establish another inverter which is selectivelyenabled based on the clock signals clk and clkb. An inverter of thetransistors P10, N10 and a transmission gate of P18, N18 couple themaster latch circuitry 104 to slave latch circuit 222. The transistorsP10, P16-P18, N10, and N16-N18 are operably coupled to form slave latchcircuit 222, while an inverter of the transistors P10, N10 and atransmission gate of the transistor P18, N18 couple the master latchcircuit 221 to the slave latch circuit 222. The transistors P16-P17 andN16-N17 establish an inverter which is selectively enabled based on theclock signals clkb and clkb. The data out circuit 223 includes aninverter of the transistors P15 and N15 and another inverter of thetransistors P12-P13 and N12-N13. Accordingly, the data output signal Qhas the same polarity (i.e., is non-inverted) with regards to theoriginal data inputs D and SI. Transistors N5, P5 make up the clockinverter 224 a while the transistors N20, P20 make up the clock inverter224 b.

The configurations of FIGS. 2A-2B are given for illustrative purposes.Various implements are within the contemplated scope of the presentdisclosure. For example, in some embodiments, the functional blocksdepicted in FIG. 2B are re-drawn. As an example, the transistors P7 andN7 are included in the scan multiplexer 210, the transistors P10, P18and N10,N18 are included in the master latch circuit 222, and thetransistors P15 and N15 are included in the slave latch circuit 222.

FIGS. 3A-3C depict several layout views of portions of the scan flipflop circuit 200 to illustrate the configurations thereof. FIGS. 3A-3Billustrate layout diagrams in a plan view of part of a front side of thescan flip flop circuit 200 in FIG. 2B, and FIG. 3C illustrates layoutdiagram and cross-section views of part of a back side of the scan flipflop circuit in FIG. 2B, according to some embodiments of the presentdisclosure. In some embodiments, the scan flip flop circuit 200 in theintegrated circuit 10 includes an active semiconductor device (i.e.,with drain/source structure implements with active areas, gatestructures, metal-on-device MD on the active areas, front side metalrouting, etc.) on its front side and some metal routing on its backside. In some embodiments, the active semiconductor device on the frontside of the scan flip flop circuit 200 is formed on a substrate (notshown) in a front side process. After the front side process iscomplete, the integrated circuit is flipped upside down, such that abackside surface of the substrate faces upwards. The substrate isfurther thinned down and removed. In some embodiments, thinning isaccomplished by a CMP process, a grinding process, or the like.Accordingly, backside process is performed to form structures on theback side of the integrated circuit 100. The details of manufacturingprocess will be discussed later.

Reference is now made to FIG. 3A. For illustration, the scan flip flopcircuit 200 is configured to be formed in a flip flop cell FFCELL1 andincludes the active areas 110-120 in a cell CELL2 in the cell row ROW1,the active areas 130-140 in a cell CELL1 in the cell row ROW2, and gatesshown as “poly” which are typically made of doped polysilicon or metal,extend over at least one of the active areas 110-140, and cover channelregions thereof. For illustration, the gates extend in y direction whilethe active areas 110-140 extend in x direction.

In some embodiments, the gates are formed by multiple cut layersseparating continuous gates, as shown in FIG. 3A. In some embodiments,the arrangements of the transistors P1-P5, P7-P13, P15-P18, P20, N1-N5,N7-N13, N15-N18, and N20 corresponding to those in FIG. 2B are shown inFIG. 3A with notations on the gates. Specifically, each of thetransistors P1-P5, P7-P10 and N1-N5, N7-N10 includes a first quantity offin structures, for example, two fin structures, formed in the activearea 130 or 140, while each of the transistors P11-P13, P15-P20 andN11-N13, N15-N20 includes a second quantity of fin structures, forexample, one fin structure, formed in the active area 120 or 110.

Reference is now made to FIG. 3B which depicts the layout of FIG. 3A ina more detailed way. As shown in FIG. 3B, the scan flip flop circuit 200includes the gates 301-328, conductive segments (or metal onoxide-definition areas (“MOOD” or “MD”)) 401-411, conductive lines (ormetal-one layer (M1)) 501-517, conductive traces (or metal-two layer(M2)) 601-603, and vias VD1-VD11, VG1-VG14, and VM1-VM8. In someembodiments, the active areas 110-140 are disposed in a first layer onthe front side of the scan flip flop circuit 200, while the gates301-328 and the conductive segments 401-411 cross at least one of theactive areas 110-140. The conductive lines 501-517 are disposed on asecond layer, above the first layer in positive z direction, on thefront side of the scan flip flop circuit 200, in which the z directionis perpendicular to both x and y directions and above the planecontaining the x- and y-axes. The vias VD1-VD11 and VG1-VG14 aredisposed between the first layer and the second layer. The conductivetraces 601-603 are disposed in a third layer, above the second layer inpositive z direction, on the front side of the scan flip flop circuit200. The vias VM1-VM8 are disposed between the second layer and thethird layer.

In some embodiments of the configurations in the front side of the scanflip flop circuit 200, as shown in the cell CELL1 in FIG. 3B, the gates302-303 correspond to gates of the transistors P1 and N1. The gate 304is shared as gates of the transistors P2 and N2. The gates 305-306correspond to gates of the transistors P3 and N3. The conductive segment401 corresponds to drains of the transistors P2-P3. The conductivesegment 402 corresponds to drains of the transistors N2-N3. The gates307-308 are shared respectively gates of the transistors P4, N4 and thetransistors P5, N5. The conductive segment 405 corresponds to drains ofthe transistors P5 and N5. The gate 310 corresponds to a gate of thetransistor P7, and the gate 311 is shared as gates of the transistor N7and P17. The conductive segment 403 corresponds to a source of thetransistor P7 and the conductive segment 411 corresponds to a source ofthe transistor N7. The gate 312 corresponds to a gate of the transistorP8, and the gate 313 is shared as gates of the transistor N8 and P18.The conductive segment 404 corresponds to drains of the transistors P7and N7 and sources of the transistors P8 and N8. The gate 314 is sharedas gates of the transistors P9 and N9. The gate 315 is shared as gatesof the transistors P10 and N10. The conductive segment 405 correspondsto drains of the transistors P10 and N10.

Furthermore, in the cell CELL2, the gate 318 is shared as gates of thetransistors P11 and N11. The conductive segment 406 corresponds todrains of the transistors P11 and N11. The gate 319 is shared as gatesof the transistors P12 and N12. The conductive segment 407 correspondsto drains of the transistors P12, P13 and N12, N13. The gate 322 isshared as gates of the transistors P15 and N15. The conductive segment408 corresponds to drains of the transistors P15 and N15. The gate 323is shared as gates of the transistors P16 and N16. The gate 324corresponds to a gate of the transistor N17, and the gate 325corresponds to a gate of the transistor N18. The gate 327 is shared asgates of the transistors P20 and N20. The conductive segment 413corresponds to drains of the transistors P20 and N20. The gates 301,309, 316-317, 321, 326, and 328 are referred to as dummy gates, in whichin some embodiments, the “dummy” gate is referred to as being notelectrically connected as the gate for MOS devices, in which the term“dummy” corresponds to having no practical function in a circuit.

For illustration, the gates 301-328 and the conductive segments 401-409extend in y direction and are separated from each other in x direction.The conductive lines 501 extend in x direction and are separated fromeach other in x or/and y direction. The conductive traces 601-603 extendin y direction and are separated from each other in x direction.

Reference is now made to FIG. 2B and FIG. 3B together. The conductivetrace 601 transmits the scan enable signal SE to the gate 302 throughthe via VM1 which is coupled between the conductive trace 601 and theconductive line 501 and the via VG1 which is coupled between theconductive line 501 and the gate 302, also to the gate 306 through thevia VM2 which is coupled between the conductive trace 601 and theconductive line 507 and the via VG5 which is coupled between theconductive line 507 and the gate 306, and to the gate 318 through thevia VM3 which is coupled between the conductive trace 601 and theconductive line 514 and the via VG10 which is coupled between theconductive line 514 and the gate 318.

The scan enable bar signal SEB is output from the conductive segment 406to the conductive trace 602 through the via VD7 which is coupled betweenthe conductive segment 406 and the conductive line 512 and the via VM6which is coupled between the conductive line 512 and the conductivetrace 602. The scan enable bar signal SEB is further transmitted to thegate 303 through the via VM5 which is coupled between the conductivetrace 602 and the conductive line 509 and the via VG2 which is coupledbetween the conductive line 509 and the gate 303, and also transmittedto the gate 305 through the via VM4 which is coupled between theconductive trace 602 and the conductive line 503 and the via VG4 whichis coupled between the conductive line 503 and the gate 305.

The conductive line 504 transmits the data signal D to the gate 304through the via VG3 which is coupled between the conductive line 504 andthe gate 304. The conductive line 505 transmits the clock signal CP tothe gate 308 through the via VG7 which is coupled between the conductiveline 505 and the gate 308.

The conductive line 508 transmits the scan data input SI to the gate 307through the via VG6 which is coupled between the conductive line 508 andthe gate 307.

The conductive segment 401 is coupled to the conductive segment 403through the via VD1 which is coupled between the conductive line 502 andthe conductive segment 401 and the via VD3 which is coupled between theconductive line 502 and the conductive segment 403. Accordingly, thedrains of the transistors P2-P3 is coupled to the source of thetransistor P7.

The conductive segment 402 is coupled to the conductive segment 411through the via VD2 coupled between the conductive line 510 and theconductive segment 402 and the via VD4 coupled between the conductiveline 510 and the conductive segment 411. Accordingly, the drains of thetransistors N2-N3 are coupled to the source of the transistor N7.

The conductive segment 404 is coupled to the conductive line 506 throughthe via VD5 and further coupled to the gate 315. Accordingly, the drainsof the transistors P7 and N7 are coupled to the gates of the transistorsP10 and N10. The conductive segment 405 is coupled to the conductiveline 513 through the via VD6, and further coupled to the gate 314through the via VG8. Accordingly, the drains of the transistors P10 andN10 are coupled to the gates of the transistors P9 and N9. Theconductive line 513 is coupled to the conductive trace 603 through thevia VM7, and the via VM8 couples the conductive trace 603 to theconductive line 516. The conductive line 516 is coupled to theconductive segment 410 through the via VD11. Therefore, the drains ofthe transistors P10 and N10 are coupled to the sources/the drains of thetransistors P18 and N18 as well.

The conductive segment 409 is coupled to the conductive line 515 throughthe via VD10, and the conductive line 515 is coupled to the gate 322through the via VG13. Accordingly, the drains/sources of the transistorsP18 and N18 are coupled to the gates of the transistors P15 and N15. Theconductive segment 408 is coupled to the conductive line 513 through thevia VD9. The conductive line 513 is coupled to the gates 319-320 and 323separately through the vias VG11-VG12 and VG14. Accordingly, the drainsof the transistors P15 and N15 are coupled to the gates of thetransistors P12-P13, P16, N12-N13, and N16.

The conductive segment 407, corresponding to the drains of thetransistors P12-P13 and N12-N13, is coupled to the conductive line 517through the via VD8. In some embodiments, the output signal Q istransmitted out from the scan flip flop circuit 200 through the routingcoupled to the conductive segment 407.

With the configurations of the FIGS. 2A-3B, the scan multiplexer 210,the master latch circuit 221, the slave latch circuit 222, and the dataout circuit 223 are configured to transmits the data signals, such asthe scan enable signal SE, the scan enable bar signal SEB, the signalsmq_x, mq, qf, and qf_x, etc, through the routing on the front side ofthe scan flip flop circuit 200, for example, the conductive segments401-411, the conductive lines 501-517, and the conductive trace 601-603.

Reference is now made to FIG. 3C. In some embodiments of theconfigurations in the back side of the scan flip flop circuit 200, theclock circuit 224 is configured to transmit the clock signals clk andclkb to the master latch circuit 221 and the slave latch circuit 222through routing on the back side of the scan flip flop circuit 200.Cross-sectional views of part of the scan flip flop circuit 200 takenalong a line B-B′ and a line C-C′ are given for better understanding ofFIG. 3C.

For illustration, the scan flip flop circuit 200 further includes backside conductive lines (i.e., back side metal one layer, “M-1”) 701-710,back side conductive lines (i.e., back side metal two layer, “M-2”)801-805, and vias VB1-VB21, VF1-VF8. In some embodiments, the back sideconductive lines 701-710 are disposed in a fourth layer below the firstlayer including the active device. The back side conductive lines801-805 are disposed in a fifth layer below the fourth layer.Alternatively stated, the fourth layer is closer to the front side ofthe scan flip flop circuit 200 than the fifth layer, and the fourthlayer is interposed between the first and fifth layers. The viasVB1-VB21 are disposed between the first layer and the fourth layer. Thevias VF1-VF8 are disposed between the fourth layer and the fifth layer.

Reference is now made to both FIGS. 2B, 3A and 3C. In some embodiments,with regard to transmitting the clock signals clkb and clk, a detailedlayout diagram of the components circled as “inter-cell back siderouting” in FIGS. 2B and 3A is presented in FIG. 3C. For example, asmentioned above, the clock signal CP is transmitted to the gate 308 ofthe transistors P5 and N5. In response to the clock signal CP, the clocksignal clkb is output at the drains of the transistors N5 and P5. Asshown in FIG. 3C, an active region 130 b, included in the active area130, corresponding to the drain of the transistor N5 is coupled to theback side conductive line 701 through the via VB1. The back sideconductive line 701 is further coupled to the gate 311, corresponding tothe gate of the transistor N7, through the via VB2. Moreover, the viaVF1 couples the back side conductive line 701 to the back sideconductive line 801. The back side conductive line 801 is coupled to theback side conductive lines 702 and 703 through the vias VF2-VF3separately. The via VB3 couples the back side conductive line 702 to thegate 312 corresponding to the gate of the transistor P8. The via VB4couples the back side conductive line 703 to the gate 325 correspondingto the gate of the transistor P18. The via VB5 further couples the backside conductive line 703 to the gate 327 corresponding to the gates ofthe transistors P20 and N20. Accordingly, the clock signal clkbgenerated by the transistors N5 and P5 is transmitted to the gates ofthe transistors N7, P8, P18, P20 and N20.

Similarly, in the embodiments of transmitting the clock signal clk, asshown in FIG. 3C, an active region 120 b, included in the active area120, corresponding to the drains of the transistors P20 and N20 iscoupled to the back side conductive line 705 through the via VB6. Theback side conductive line 705 is further coupled to the gate 313,corresponding to the gates of the transistors N8 and P18, through thevia VB7. Moreover, the via VF4 couples the back side conductive line 705to the back side conductive line 802. The back side conductive line 802is coupled to the back side conductive lines 710 and 704 through thevias VF5-VF6 separately. The via VB5 couples the back side conductiveline 710 to the gate 324 corresponding to the gate of the transistorP17. The via VB9 couples the back side conductive line 704 to the gate310 corresponding to the gate of the transistor P7. Accordingly, theclock signal clk generated by the transistors N20 and P20 is transmittedto the gates of the transistors P7, N8, P17 and N18.

In some embodiments, the scan flip flop circuit 200 also receives supplyvoltages from the back side routing. For illustration, the back sideconductive lines 803 and 805 are configured to input a supply voltageVSS (i.e., usually referred to as a ground voltage) for the scan flipflop circuit 200, and the back side conductive line 804 is configured toinput a supply voltage VDD, greater than the supply voltage VSS.Furthermore, the via VF7 is coupled between the back side conductiveline 803 and the back side conductive line 707 to transmit the supplyvoltage VSS to the back side conductive line 707. The via VF8 is coupledbetween the back side conductive line 804 and the back side conductiveline 706 to transmit the supply voltage VDD to the back side conductiveline 707.

As aforementioned, with reference to both FIGS. 2B and 3C, an activeregion 140 a, corresponding to the source of the transistor P1, receivesthe supply voltage VDD through the via VB10 coupled between the activeregion 140 a and the back side conductive line 706. An active region 130a, corresponding to the source of the transistor N1, receives the supplyvoltage VSS through the via VB11 coupled between the active region 130 aand the back side conductive line 707. An active region 140 b,corresponding to the sources of the transistors P4-P5, receives thesupply voltage VDD through the via VB12 coupled between the activeregion 140 b and the back side conductive line 706. An active region 130b, corresponding to the sources of the transistors N4-N5, receives thesupply voltage VSS through the via VB13 coupled between the activeregion 130 b and the back side conductive line 707. Similarly, activeregions 120 a-120 c, corresponding to the sources of the transistorsN11-N13 and N15-N16 separately, receive the supply voltage VSS throughthe vias VB14, VB16, and VB18, in which the vias VB14, VB16, and VB18couple the back side conductive line 707 to the active regions 120 a-120c separately.

In some embodiments, the flip flop cell FFCELL1 shares some of the backside conductive lines 701-710 with other abutting flip flop cell (notshown, will be discussed in the following paragraphs). The back sideconductive line 708 provides the supply voltage VDD received from otherflip flop cell, and accordingly, active regions 110 a-110 c,corresponding to the sources of the transistors P11-P13 and P15-P16separately, receive the supply voltage VDD through the vias VB15, VB17,and VB19, in which the vias VB15, VB17, and VB19 couple the back sideconductive line 708 to the active regions 110 a-110 c separately.Similarly, the back side conductive line 709 provides the supply voltageVSS received from other flip flop cell, and accordingly, active regions130 d and 120 e, corresponding to the sources of the transistors N10 andN20 separately, receive the supply voltage VSS through the vias VB20 andVB21, in which the vias VB20 and VB21 couple the back side conductiveline 709 to the active regions 130 d and 120 e separately.

Based on the above descriptions, the back side conductive lines, suchlike the back side conductive lines 706-709 and 803-805, configured totransmit the supply voltages VDD and VSS are referred to as power rails.In some embodiments, the back side conductive lines configured totransmit the clock signals clk and clkb are surrounded by or disposedbeside the power rails in the same layer on the back side of the scanflip flop circuit 200 in a layout view. For example, as shown in FIG.3C, at least one, such as the back side conductive lines 706-709, of theback side conductive lines 701-709 includes a first portion(s) extendingin x direction and a second portion(s) extending in y direction.Alternatively stated, at least one of the back side conductive lines706-709 is L-shaped. The back side conductive lines 801-805 extend in ydirection. Accordingly, the back side conductive line 706 surrounds theback side conductive lines 702 and 704. The back side conductive lines701 and 705 are interposed between the back side conductive lines 707and 709. Furthermore, the back side conductive lines 801-802 areinterposed between the back side conductive lines 804-805 in the fifthlayer on the back side of the scan flip flop circuit 200.

In some approaches, clock signals are transmitted through metal routingon the front side of the integrated circuit while other data signalspassing in proximate conductive lines. In such arrangements, the clocksignals are vulnerable to be interfered by those data signals because ofno shielding. In the embodiments of the present disclosure, by arrangingthe conductive lines configured to transmit the clock signals on theback side and interposed between the power rails on the back side, thepower rails function as shielding to enhance noise immunity of the backside conductive lines while transmitting the clock signals.

The configurations of FIGS. 3A-3C are given for illustrative purposes.Various implements are within the contemplated scope of the presentdisclosure. For example, in some embodiments, there is further a viacoupled between the back side conductive line 706 and an active region,corresponding the source of the transistor P10, to transmit the supplyvoltage VDD to the transistor P10. In various embodiments, a portion ofa conductive line, configured with respect to the back side conductiveline 708, overlaps the back side conductive line 805 and a via couplesthe portion of the conductive line to active region, corresponding thesource of the transistor P20, to transmit the supply voltage VDD to thetransistor P20.

Reference is now made to FIG. 4. FIG. 4 is a layout diagram in a planview of part of an integrated circuit 40, in accordance with variousembodiments. With respect to the embodiments of FIGS. 1-3C, likeelements in FIG. 4 are designated with the same reference numbers forease of understanding. The specific operations of similar elements,which are already discussed in detail in above paragraphs, are omittedherein for the sake of brevity.

As shown in FIG. 4, the integrated circuit 40 includes multiple flipflop cells FFCELL1-FFCELL2 which have the same configurations. The flipflop cell FFCELL2 abuts the flip flop cell FFCELL1 in y direction. Theflip flop cells FFCELL1-FFCELL2 are arranged in the cell rows havingmixed cell heights which have the configurations similar to theintegrated circuit 10 in FIG. 1A. Hence, the repetitious descriptionsare omitted here.

In some embodiments, the flip flop cells FFCELL1-FFCELL2 are arrangedalong other cells in the integrated circuit 40 and share the back sideconductive lines 706-709, 707′, 708′, 708″, and 709′. For illustration,the back side conductive lines 706-709, 707′, 708′, 708″, and 709′extend in x direction and pass the cell arranged in the cell rows. Inaddition, the back side conductive lines 706, 708, 708′, and 708″receive the supply voltage VDD through the vias coupling to the backside conductive lines 804, 807, and 808. The back side conductive lines707, 707′, 709, and 709′ receive the supply voltage VSS through the viascoupling to the back side conductive lines 803, 806, and 809.Alternatively stated, the flip flop cells FFCELL1-FFCELL2 also share theback side conductive lines 803-805 as the back side conductive lines803-805 extend in y direction and pass through the flip flop cellsFFCELL1-FFCELL2.

The configurations of FIG. 4 are given for illustrative purposes.Various implements are within the contemplated scope of the presentdisclosure. For example, in some embodiments, there are vias couplingthe back side conductive lines 709 and 709′ to the back side conductiveline 805.

Reference is now made to FIG. 5. FIG. 5 illustrates layout diagram andcross-section views of part of an integrated circuit 50, in accordancewith various embodiments. With respect to the embodiments of FIGS. 1-4,like elements in FIG. 5 are designated with the same reference numbersfor ease of understanding. In some embodiments, the integrated circuit50 is configured with respect to, for example, the integrated circuit 40in FIG. 4. For the sake of brevity, the flip flop cells are not shown inthe diagram. Cross-sectional views of part of the integrated circuit 50taken along a line D-D′ and a line E-E′ are given for betterunderstanding of FIG. 5.

Compared with FIG. 4, the integrated circuit 50 further includes backside conductive traces (i.e., back side metal three layer, “M-3”)901-905, back side conductive traces (i.e., back side metal four layer,“M-4”) 1001-1007, and vias VC and VT. In some embodiments, the back sideconductive traces 901-905 are disposed in a sixth layer below the fifthlayer on the back side of the integrated circuit 50. The back sideconductive traces 1001-1007 are disposed in a seventh layer below thesixth layer on the back side of the integrated circuit 50. The vias VCare disposed between the fifth and sixth layers on the back side of theintegrated circuit 50. The vias VT are disposed between the sixth andseven layers on the back side of the integrated circuit 50.

For illustration, the back side conductive traces 901-905 extend in xdirection and are separated from each other in y direction. The backside conductive traces 1001-1007 extend in y direction and are separatedfrom each other in x direction.

In some embodiments, the back side conductive traces 1001-1007 areconfigured to transmit the supply voltages VDD and VSS to the back sideconductive lines 706-709, 707′, 708′, 708″, and 709′ through the backside conductive line 803-809 and the back side conductive trace 901-905.For example, the back side conductive trace 1002 provides the supplyvoltage VDD to the back side conductive trace 902 through the vias VT.The back side conductive trace 902 couples to the back side conductiveline 807 through the via VC. The back side conductive line 807 furtheris coupled to the 706 through the via VF. Accordingly, the supplyvoltage VDD is transmitted from the back side conductive trace 1002 tothe back side conductive line 706 and further to the active devices.

Taking another example, along line E-E′, the back side conductive trace1003 is coupled to the back side conductive trace 901 through the viaVT, and the back side conductive trace 901 is coupled to the back sideconductive line 803 through the via VC. Moreover, with reference to bothFIGS. 3C and 5, the back side conductive line 803 is coupled to the backside conductive line 707 through the via VF7. The back side conductiveline 707 is coupled to the flip flop cell FFCELL1 through the via VB11.Accordingly, the supply voltage VSS is transmitted from the back sideconductive trace 1003 to the flip flop cell FFCELL1. The configurationsof the back side conductive traces 901-905 and the back side conductivetraces 1001-1007 are similar to that of the back side conductive trace902 and the back side conductive trace 1003. Hence, the repetitiousdescriptions are omitted here.

In some approaches, while clock signals are shared with multiple flipflop cells by the metal routing on the front side of an integratedcircuit, it results in a circuit design of great complexity and areapenalty. As shown in FIGS. 4 and 5, as power supply voltages and theclock signals are transmitted through the metal lines on the back side,an improved flexibility and utilization of routing is provided, andthus, the circuit design is optimized and the manufacturing cost is cut.

The configurations of FIG. 5 are given for illustrative purposes.Various implements are within the contemplated scope of the presentdisclosure. For example, in some embodiments, the number of the vias VCand VT is greater than that shown in FIG. 5.

FIG. 6 is a flow chart of a method 1100 of fabricating an integratedcircuit including the integrated circuit 10, 40, or 50, in accordancewith some embodiments of the present disclosure. It is understood thatadditional operations can be provided before, during, and after theprocesses shown by FIG. 6, and some of the operations described belowcan be replaced or eliminated, for additional embodiments of the method.The order of the operations/processes may be interchangeable. Throughoutthe various views and illustrative embodiments, like reference numbersare used to designate like elements. The method 1100 includes operations1110-1150 that are described below with reference to the flip flopcircuit 200 of FIGS. 3B-3C.

In operation 1110, the active device operating as the scan flip flopcircuit 200 is formed on the front side of the integrated circuit 10, asshown in FIG. 3B. The active device includes active components, such asthe transistors P1-P5, P7-P13, P15-P18, P20, N1-N5, N7-N13, N15-N18, andN20.

In some embodiments, after the active device is formed, the integratedcircuit is flipped upside down for the back side processes.

In operation 1120, the back side conductive lines including, forexample, the back side conductive lines 701-705 and 710, are formed toextend in x direction in the fourth layer (i.e., the layer below thefirst layer on the front side of the scan flip flop circuit 200, asmentioned above) on the back side of the integrated circuit 10 totransmit the clock signals clk and clkb to the scan flip flop circuit200, as shown in FIG. 3C.

In operation 1130, other back side conductive lines including, forexample, the back side conductive lines 706-709, are formed in thefourth layer on the back side of the integrated circuit 10 to transmitthe supply voltages VSS and VDD to the scan flip flop circuit 200. Asshown in FIG. 3C, for example, the back side conductive lines 701 and705 are interposed between the back side conductive lines 707 and 709.The back side conductive lines 702 and 704 are surrounded by the backside conductive line 706.

In some embodiments, at least one of the back side conductive lines706-709 includes a first portion extending in x direction and a secondportion extending in y direction, for example, the back side conductiveline 707 having a L shape.

In operation 1140, the back side conductive lines 801-802 are formed toextend in y direction in the fifth layer (i.e., the layer below thefourth layer on the back side of the scan flip flop circuit 200, asmentioned above) on the back side of the integrated circuit 10, as shownin FIG. 3C. The fourth layer is interposed between the fifth layer onthe back side and the front side of the integrated circuit 10. The backside conductive lines 801-802 are configured to transmit the clocksignals clk and clkb between the back side conductive lines 701-705 and710.

In operation 1150, the back side conductive lines 803-805 extendingparallel to the back side conductive lines 801-802 are formed in thefifth layer on the back side of the integrated circuit 10 to transmitthe supply voltages VSS and VDD to the back side conductive lines706-709, as shown in FIG. 3C. In some embodiments, the back sideconductive lines 801-802 are interposed between the back side conductivelines 804 and 805.

In some embodiments, as shown in FIG. 5, the method 1100 furtherincludes forming the back side conductive traces 901-905 extending in xdirection in the sixth layer (i.e., the layer below the fifth layer onthe back side of the scan flip flop circuit 200, as mentioned above) andthe back side conductive traces 1001-1007 extending in y direction inthe seventh layer (i.e., the layer below the sixth layer on the backside of the scan flip flop circuit 200, as mentioned above). Forexample, the back side conductive traces 901-905 and the back sideconductive traces 1001-1007 are configured to transmit the supplyvoltages VSS and BDD to the back side conductive lines 803-804.

In some embodiment, there are no conductive line in the sixth andseventh layers on the back side of the integrated circuit 10 configuredto transmit the clock signals clk and clkb, as shown in the crosssectional views in the FIG. 5.

Reference is now made to FIG. 7. FIG. 7 is a block diagram of anelectronic design automation (EDA) system 1200 for designing theintegrated circuit layout design, in accordance with some embodiments ofthe present disclosure. EDA system 1200 is configured to implement oneor more operations of the method 1100 disclosed in FIG. 6, and furtherexplained in conjunction with FIGS. 1A-5. In some embodiments, EDAsystem 1200 includes an APR system.

In some embodiments, EDA system 1200 is a general purpose computingdevice including a hardware processor 1202 and a non-transitory,computer-readable storage medium 1204. Storage medium 1204, amongstother things, is encoded with, i.e., stores, computer program code(instructions) 1206, i.e., a set of executable instructions. Executionof instructions 1206 by hardware processor 1202 represents (at least inpart) an EDA tool which implements a portion or all of, e.g., the method1100.

The processor 1202 is electrically coupled to computer-readable storagemedium 1204 via a bus 1208. The processor 1202 is also electricallycoupled to an I/O interface 1210 and a fabrication tool 1216 by bus1208. A network interface 1212 is also electrically connected toprocessor 1202 via bus 1208. Network interface 1212 is connected to anetwork 1214, so that processor 1202 and computer-readable storagemedium 1204 are capable of connecting to external elements via network1214. The processor 1202 is configured to execute computer program code1206 encoded in computer-readable storage medium 1204 in order to causeEDA system 1200 to be usable for performing a portion or all of thenoted processes and/or methods. In one or more embodiments, processor1202 is a central processing unit (CPU), a multi-processor, adistributed processing system, an application specific integratedcircuit (ASIC), and/or a suitable processing unit.

In one or more embodiments, computer-readable storage medium 1204 is anelectronic, magnetic, optical, electromagnetic, infrared, and/or asemiconductor system (or apparatus or device). For example,computer-readable storage medium 1204 includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a randomaccess memory (RAM), a read-only memory (ROM), a rigid magnetic disk,and/or an optical disk. In one or more embodiments using optical disks,computer-readable storage medium 1204 includes a compact disk-read onlymemory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digitalvideo disc (DVD).

In one or more embodiments, storage medium 1204 stores computer programcode 1206 configured to cause EDA system 1200 (where such executionrepresents (at least in part) the EDA tool) to be usable for performinga portion or all of the noted processes and/or methods. In one or moreembodiments, storage medium 1204 also stores information whichfacilitates performing a portion or all of the noted processes and/ormethods. In one or more embodiments, storage medium 1204 stores IClayout diagram 1220 of standard cells including such standard cells asdisclosed herein, for example, cells corresponding to the integratedcircuits 10, 40, and 50 discussed above with respect to FIGS. 1A-5.

EDA system 1200 includes I/O interface 1210. I/O interface 1210 iscoupled to external circuitry. In one or more embodiments, I/O interface1210 includes a keyboard, keypad, mouse, trackball, trackpad,touchscreen, and/or cursor direction keys for communicating informationand commands to processor 1202.

EDA system 1200 also includes network interface 1212 coupled toprocessor 1202. Network interface 1212 allows EDA system 1200 tocommunicate with network 1214, to which one or more other computersystems are connected. Network interface 1212 includes wireless networkinterfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wirednetwork interfaces such as ETHERNET, USB, or IEEE-1264. In one or moreembodiments, a portion or all of noted processes and/or methods areimplemented in two or more systems 1200.

EDA system 1200 also includes the fabrication tool 1216 coupled toprocessor 1202. The fabrication tool 1216 is configured to fabricateintegrated circuits, e.g., the integrated circuits 10, 40, and 50discussed above with respect to FIGS. 1A-5, according to the designfiles processed by the processor 1202.

EDA system 1200 is configured to receive information through I/Ointerface 1210. The information received through I/O interface 1210includes one or more of instructions, data, design rules, libraries ofstandard cells, and/or other parameters for processing by processor1202. The information is transferred to processor 1202 via bus 1208. EDAsystem 1200 is configured to receive information related to a UI throughI/O interface 1210. The information is stored in computer-readablemedium 1204 as design specification 1222.

In some embodiments, a portion or all of the noted processes and/ormethods are implemented as a standalone software application forexecution by a processor. In some embodiments, a portion or all of thenoted processes and/or methods are implemented as a software applicationthat is a part of an additional software application. In someembodiments, a portion or all of the noted processes and/or methods areimplemented as a plug-in to a software application. In some embodiments,at least one of the noted processes and/or methods are implemented as asoftware application that is a portion of an EDA tool. In someembodiments, a portion or all of the noted processes and/or methods areimplemented as a software application that is used by EDA system 1200.In some embodiments, a layout diagram which includes standard cells isgenerated using a suitable layout generating tool.

In some embodiments, the processes are realized as functions of aprogram stored in a non-transitory computer readable recording medium.Examples of a non-transitory computer readable recording medium include,but are not limited to, external/removable and/or internal/built-instorage or memory unit, for example, one or more of an optical disk,such as a DVD, a magnetic disk, such as a hard disk, a semiconductormemory, such as a ROM, a RAM, a memory card, and the like.

FIG. 8 is a block diagram of IC manufacturing system 1300, and an ICmanufacturing flow associated therewith, in accordance with someembodiments. In some embodiments, based on a layout diagram, at leastone of (A) one or more semiconductor masks or (B) at least one componentin a layer of a semiconductor integrated circuit is fabricated using ICmanufacturing system 1300.

In FIG. 8, IC manufacturing system 1300 includes entities, such as adesign house 1320, a mask house 1330, and an IC manufacturer/fabricator(“fab”) 1350, that interact with one another in the design, development,and manufacturing cycles and/or services related to manufacturing an ICdevice 1360. The entities in IC manufacturing system 1300 are connectedby a communications network. In some embodiments, the communicationsnetwork is a single network. In some embodiments, the communicationsnetwork is a variety of different networks, such as an intranet and theInternet. The communications network includes wired and/or wirelesscommunication channels. Each entity interacts with one or more of theother entities and provides services to and/or receives services fromone or more of the other entities. In some embodiments, two or more ofdesign house 1320, mask house 1330, and IC fab 1350 is owned by a singleentity. In some embodiments, two or more of design house 1320, maskhouse 1330, and IC fab 1350 coexist in a common facility and use commonresources.

Design house (or design team) 1320 generates an IC design layout diagram1322. IC design layout diagram 1322 includes various geometricalpatterns, for example, an IC layout design depicted in FIGS. 1A, and3A-5, designed for an IC device 1360, for example, the integratedcircuits 10, 40, and 50 discussed above with respect to FIGS. 1A, and3A-5. The geometrical patterns correspond to patterns of metal, oxide,or semiconductor layers that make up the various components of IC device1360 to be fabricated. The various layers combine to form various ICfeatures. For example, a portion of IC design layout diagram 1322includes various IC features, such as an active region, gate electrode,source and drain, conductive segments or vias of an interlayerinterconnection, to be formed in a semiconductor substrate (such as asilicon wafer) and various material layers disposed on the semiconductorsubstrate. Design house 1320 implements a proper design procedure toform IC design layout diagram 1322. The design procedure includes one ormore of logic design, physical design or place and route. IC designlayout diagram 1322 is presented in one or more data files havinginformation of the geometrical patterns. For example, IC design layoutdiagram 1322 can be expressed in a GDSII file format or DFII fileformat.

Mask house 1330 includes data preparation 1332 and mask fabrication1344. Mask house 1330 uses IC design layout diagram 1322 to manufactureone or more masks 1345 to be used for fabricating the various layers ofIC device 1360 according to IC design layout diagram 1322. Mask house1330 performs mask data preparation 1332, where IC design layout diagram1322 is translated into a representative data file (“RDF”). Mask datapreparation 1332 provides the RDF to mask fabrication 1344. Maskfabrication 1344 includes a mask writer. A mask writer converts the RDFto an image on a substrate, such as a mask (reticle) 1345 or asemiconductor wafer 1353. The IC design layout diagram 1322 ismanipulated by mask data preparation 1332 to comply with particularcharacteristics of the mask writer and/or requirements of IC fab 1350.In FIG. 8, data preparation 1332 and mask fabrication 1344 areillustrated as separate elements. In some embodiments, data preparation1332 and mask fabrication 1344 can be collectively referred to as maskdata preparation.

In some embodiments, data preparation 1332 includes optical proximitycorrection (OPC) which uses lithography enhancement techniques tocompensate for image errors, such as those that can arise fromdiffraction, interference, other process effects and the like. OPCadjusts IC design layout diagram 1322. In some embodiments, datapreparation 1332 includes further resolution enhancement techniques(RET), such as off-axis illumination, sub-resolution assist features,phase-shifting masks, other suitable techniques, and the like orcombinations thereof. In some embodiments, inverse lithographytechnology (ILT) is also used, which treats OPC as an inverse imagingproblem.

In some embodiments, data preparation 1332 includes a mask rule checker(MRC) that checks the IC design layout diagram 1322 that has undergoneprocesses in OPC with a set of mask creation rules which contain certaingeometric and/or connectivity restrictions to ensure sufficient margins,to account for variability in semiconductor manufacturing processes, andthe like. In some embodiments, the MRC modifies the IC design layoutdiagram 1322 to compensate for limitations during mask fabrication 1344,which may undo part of the modifications performed by OPC in order tomeet mask creation rules.

In some embodiments, data preparation 1332 includes lithography processchecking (LPC) that simulates processing that will be implemented by ICfab 1350 to fabricate IC device 1360. LPC simulates this processingbased on IC design layout diagram 1322 to create a simulatedmanufactured device, such as IC device 1360. The processing parametersin LPC simulation can include parameters associated with variousprocesses of the IC manufacturing cycle, parameters associated withtools used for manufacturing the IC, and/or other aspects of themanufacturing process. LPC takes into account various factors, such asaerial image contrast, depth of focus (“DOF”), mask error enhancementfactor (“MEEF”), other suitable factors, and the like or combinationsthereof. In some embodiments, after a simulated manufactured device hasbeen created by LPC, if the simulated device is not close enough inshape to satisfy design rules, OPC and/or MRC are be repeated to furtherrefine IC design layout diagram 1322.

It should be understood that the above description of data preparation1332 has been simplified for the purposes of clarity. In someembodiments, data preparation 1332 includes additional features such asa logic operation (LOP) to modify the IC design layout diagram 1322according to manufacturing rules. Additionally, the processes applied toIC design layout diagram 1322 during data preparation 1332 may beexecuted in a variety of different orders.

After data preparation 1332 and during mask fabrication 1344, a mask1345 or a group of masks 1345 are fabricated based on the modified ICdesign layout diagram 1322. In some embodiments, mask fabrication 1344includes performing one or more lithographic exposures based on ICdesign layout diagram 1322. In some embodiments, an electron-beam(e-beam) or a mechanism of multiple e-beams is used to form a pattern ona mask (photomask or reticle) 1345 based on the modified IC designlayout diagram 1322. Mask 1345 can be formed in various technologies. Insome embodiments, mask 1345 is formed using binary technology. In someembodiments, a mask pattern includes opaque regions and transparentregions. A radiation beam, such as an ultraviolet (UV) beam, used toexpose the image sensitive material layer (for example, photoresist)which has been coated on a wafer, is blocked by the opaque region andtransmits through the transparent regions. In one example, a binary maskversion of mask 1345 includes a transparent substrate (for example,fused quartz) and an opaque material (for example, chromium) coated inthe opaque regions of the binary mask. In another example, mask 1345 isformed using a phase shift technology. In a phase shift mask (PSM)version of mask 1345, various features in the pattern formed on thephase shift mask are configured to have proper phase difference toenhance the resolution and imaging quality. In various examples, thephase shift mask can be attenuated PSM or alternating PSM. The mask(s)generated by mask fabrication 1344 is used in a variety of processes.For example, such a mask(s) is used in an ion implantation process toform various doped regions in semiconductor wafer 1353, in an etchingprocess to form various etching regions in semiconductor wafer 1353,and/or in other suitable processes.

IC fab 1350 includes wafer fabrication 1352. IC fab 1350 is an ICfabrication business that includes one or more manufacturing facilitiesfor the fabrication of a variety of different IC products. In someembodiments, IC Fab 1350 is a semiconductor foundry. For example, theremay be a manufacturing facility for the front end fabrication of aplurality of IC products (front-end- of-line (FEOL) fabrication), whilea second manufacturing facility may provide the back end fabrication forthe interconnection and packaging of the IC products (back-end-of-line(BEOL) fabrication), and a third manufacturing facility may provideother services for the foundry business.

IC fab 1350 uses mask(s) 1345 fabricated by mask house 1330 to fabricateIC device 1360. Thus, IC fab 1350 at least indirectly uses IC designlayout diagram 1322 to fabricate IC device 1360. In some embodiments,semiconductor wafer 1353 is fabricated by IC fab 1350 using mask(s) 1345to form IC device 1360. In some embodiments, the IC fabrication includesperforming one or more lithographic exposures based at least indirectlyon IC design layout diagram 1322. Semiconductor wafer 1353 includes asilicon substrate or other proper substrate having material layersformed thereon. Semiconductor wafer 1353 further includes one or more ofvarious doped regions, dielectric features, multilevel interconnects,and the like (formed at subsequent manufacturing steps).

As described above, integrated circuits in the present disclosureinclude back side conductive lines for transmitting clock signals andsupply voltage signals. With the configurations of the presentdisclosure, the noise disturbance induced by data signals transmitted ona front side of the integrated circuit is eliminated while theconductive lines for the clock signals are not proximate to the datasignals and the conductive lines for supply voltage signals shield theconductive lines for the clock signals from disturbance. Hence, anenhanced noise immunity of the integrated circuit is provided.

In some embodiments, an integrated circuit is disclosed, including afirst latch circuit, a second latch circuit, and a clock circuit. Thefirst latch circuit transmits multiple data signals to the second latchcircuit through multiple first conductive lines disposed on a front sideof the integrated circuit. The clock circuit transmits a first clocksignal and a second clock signal to the first latch circuit and thesecond latch circuit through multiple second conductive lines disposedon a backside, opposite of the front side, of the integrated circuit. Insome embodiments, the clock circuit includes a first inverter configuredto generate the first clock signal. Each transistor in the firstinverter includes a first quantity of fin structures. The clock circuitalso includes a second inverter configured to generate the second clocksignal. Each transistor in the second inverter includes a secondquantity of fin structures. The first quantity and the second quantityare different from each other. In some embodiments, the secondconductive lines include a first group of conductive lines disposed in afirst layer on the back side of the integrated circuit and a secondgroup of conductive lines disposed in a second layer on the back side ofthe integrated circuit. The first layer is closer to the front side ofthe integrated circuit than the second layer. In some embodiments, theintegrated circuit further includes at least one first via coupledbetween at least one of the first group of conductive lines and at leastone of the second group of conductive lines and at least one second viacoupled between the at least one of the first group of conductive linesand at least one gate included in the first latch circuit. In someembodiments, the integrated circuit further includes multiple powerrails disposed in the first layer. The first group of conductive linesare interposed between the power rails. In some embodiments, theintegrated circuit further includes multiple first power rails. Thefirst power rails and the second conductive lines are disposed in afirst layer on the back side of the integrated circuit. At least one ofthe first power rails includes a first portion extending in a firstdirection and a second portion extending in a second direction differentfrom the first direction. The at least one of the first power railssurrounds at least one of the second conductive lines in a layout view.In some embodiments, the integrated circuit further includes multiplesecond power rails extending in the second direction and separate fromeach other in the first direction and multiple vias coupled between thefirst power rails and the second power rails. In some embodiments, theintegrated circuit further includes multiple power rails disposed in afirst layer on the back side of the integrated circuit. At least one ofthe power rails is L-shaped. The power rails are configured to transmita first supply voltage and a second supply voltage to the first latchcircuit and the second latch circuit. In some embodiments, theintegrated circuit further includes multiple first power rails tomultiple fourth power rails disposed in first to fourth layers on theback side of the integrated circuit. The first layer is the closest one,of the first to fourth layers, to the front side of the integratedcircuit and the fourth layer is the farthest one, of the first to fourthlayers, from the front side of the integrated circuit. The first powerrails to the fourth power rails are configured to transmit at least onesupply voltage to the first latch circuit, the second latch circuit, andthe clock circuit. In some embodiments, the second conductive linesincluding a first group of conductive lines disposed in the first layerand interposed between the first power rails in a layout view and asecond group of conductive lines disposed in the second layer andinterposed between the second power rails in the layout view.

Also disclosed is an integrated circuit that includes a flip flopcircuit including a first cell having a first cell height and a secondcell having a second cell height. The flip flop circuit includes a firsttransistor in the first cell and a second transistor in the second cell.The first transistor includes a first gate and a first active region.The first gate receives a first signal from a first conductive linedisposed on a front side of the integrated circuit. The first activeregion transmits a first clock signal, according to the first signal, toa second conductive line in a first layer on a back side, opposite tothe front side, of the integrated circuit. The flip flop circuit furtherincludes a third conductive line disposed in a second layer, below thefirst layer, on the back side of the integrated circuit and coupled tothe second conductive line. The second transistor includes a second gateand a second active region. The second gate receives the first clocksignal through a fourth conductive line which is disposed in the firstlayer on the back side of the integrated circuit and coupled to thethird conductive line. The second active region transmits a second clocksignal, according to the first clock signal, to a fifth conductive linein the first layer on the back side of the integrated circuit, in whichthe second clock signal is generated by inverting the first clocksignal. In some embodiments, the first cell height and the second cellheight are different from each other. In some embodiments, theintegrated circuit further includes a first power rail and a secondpower rail that are disposed in the first layer on the back side of theintegrated circuit. The first power rail couples a third active regionincluded in the first transistor to a first supply voltage. The secondpower rail couples a fourth active region included in the secondtransistor to the first supply voltage. The second conductive line isinterposed between the first power rail and the second power rail. Insome embodiments, the integrated circuit further includes multiple theflip flop circuits in multiple flip flop cells. The flip flop cells abuteach other along a direction. The integrated circuit further includes athird power rail and a fourth power rail that are disposed in the secondlayer on the back side of the integrated circuit and pass through theflip flop cells in the direction. The third power rail and the fourthpower rail are configured to couple, respectively, the first power railand the second power rail to the first supply voltage. In someembodiments, the third conductive line extends across the first cell tothe second cell. In some embodiments, the integrated circuit furtherincludes a third transistor in the first cell. The third transistorincludes a third gate configured to receive the first clock signalthrough a sixth conductive line which is disposed in the first layer onthe back side of the integrated circuit and coupled to the thirdconductive line.

Also disclosed is a method including the following operations: formingan active device operating as a scan flip flop circuit on a front sideof an integrated circuit; forming multiple first conductive linesextending in a first direction in a first layer on a back side of theintegrated circuit to transmit a first clock signal and a second clocksignal to the active device; forming multiple second conductive lines inthe first layer on the back side of the integrated circuit to transmit afirst supply voltage and a second supply voltage to the active device,in which the first conductive lines are interposed between the secondconductive lines; forming multiple third conductive lines extending in asecond direction different from the first direction in a second layer onthe back side of the integrated circuit to transmit the first clocksignal and the second clock signal between the first conductive lines,in which the first layer is disposed between the second layer and thefront side of the integrated circuit; and forming multiple fourthconductive lines extending parallel to the third conductive lines in thesecond layer on the back side of the integrated circuit to transmit thefirst supply voltage and the second supply voltage to the secondconductive lines, in which the third conductive lines are interposedbetween the fourth conductive lines. In some embodiments, at least oneof the second conductive lines includes a first portion extending in thefirst direction and a second portion extending in the second direction.In some embodiments, the method further includes forming multiple fifthconductive lines extending in the first direction and multiple sixthconductive lines extending in the second direction in a third layer anda fourth layer, respectively, on the back side of the integrated circuitto transmit the first supply voltage and the second supply voltage tothe fourth conductive lines. In some embodiments, the third layer issandwiched between the second layer and the fourth layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit, comprising: a first latchcircuit and a second latch circuit, wherein the first latch circuit isconfigured to transmit a plurality of data signals to the second latchcircuit through a plurality of first conductive lines disposed on afront side of the integrated circuit; and a clock circuit configured totransmit a first clock signal and a second clock signal to the firstlatch circuit and the second latch circuit through a plurality of secondconductive lines disposed on a backside, opposite of the front side, ofthe integrated circuit.
 2. The integrated circuit of claim 1, whereinthe clock circuit comprises: a first inverter configured to generate thefirst clock signal, wherein each transistor in the first inverterincludes a first quantity of fin structures; and a second inverterconfigured to generate the second clock signal, wherein each transistorin the second inverter includes a second quantity of fin structures,wherein the first quantity and the second quantity are different fromeach other.
 3. The integrated circuit of claim 1, wherein the pluralityof second conductive lines comprise: a first group of conductive linesdisposed in a first layer on the back side of the integrated circuit;and a second group of conductive lines disposed in a second layer on theback side of the integrated circuit, wherein the first layer is closerto the front side of the integrated circuit than the second layer. 4.The integrated circuit of claim 3, further comprising: at least onefirst via coupled between at least one of the first group of conductivelines and at least one of the second group of conductive lines; and atleast one second via coupled between the at least one of the first groupof conductive lines and at least one gate included in the first latchcircuit.
 5. The integrated circuit of claim 3, further comprising: aplurality of power rails disposed in the first layer, wherein the firstgroup of conductive lines are interposed between the plurality of powerrails.
 6. The integrated circuit of claim 1, further comprising: aplurality of first power rails, wherein the plurality of first powerrails and the plurality of second conductive lines are disposed in afirst layer on the back side of the integrated circuit, wherein at leastone of the plurality of first power rails includes a first portionextending in a first direction and a second portion extending in asecond direction different from the first direction, wherein the atleast one of the plurality of first power rails surrounds at least oneof the plurality of second conductive lines in a layout view.
 7. Theintegrated circuit of claim 6, further comprising: a plurality of secondpower rails extending in the second direction and separate from eachother in the first direction; and a plurality of vias coupled betweenthe plurality of first power rails and the plurality of second powerrails.
 8. The integrated circuit of claim 1, further comprising: aplurality of power rails disposed in a first layer on the back side ofthe integrated circuit, wherein at least one of the plurality of powerrails is L-shaped, wherein the plurality of power rails are configuredto transmit a first supply voltage and a second supply voltage to thefirst latch circuit and the second latch circuit.
 9. The integratedcircuit of claim 1, further comprising: a plurality of first power railsto a plurality of fourth power rails disposed in first to fourth layerson the back side of the integrated circuit, wherein the plurality offirst power rails to the plurality of fourth power rails are configuredto transmit at least one supply voltage to the first latch circuit, thesecond latch circuit, and the clock circuit.
 10. The integrated circuitof claim 9, wherein the plurality of second conductive lines comprise: afirst group of conductive lines disposed in the first layer andinterposed between the plurality of first power rails in a layout view;and a second group of conductive lines disposed in the second layer andinterposed between the plurality of second power rails in the layoutview.
 11. An integrated circuit, comprising: a flip flop circuitincluding a first cell having a first cell height and a second cellhaving a second cell height, and comprising: a first transistor in thefirst cell, comprising: a first gate configured to receive a firstsignal from a first conductive line disposed on a front side of theintegrated circuit; and a first active region configured to transmit afirst clock signal, according to the first signal, to a secondconductive line in a first layer on a back side, opposite to the frontside, of the integrated circuit; a third conductive line disposed in asecond layer, below the first layer, on the back side of the integratedcircuit and coupled to the second conductive line; and a secondtransistor in the second cell, comprising: a second gate configured toreceive the first clock signal through a fourth conductive line which isdisposed in the first layer on the back side of the integrated circuitand coupled to the third conductive line; and a second active regionconfigured to transmit a second clock signal, according to the firstclock signal, to a fifth conductive line in the first layer on the backside of the integrated circuit, wherein the second clock signal isgenerated by inverting the first clock signal.
 12. The integratedcircuit of claim 11, wherein the first cell height and the second cellheight are different from each other.
 13. The integrated circuit ofclaim 11, further comprising: a first power rail and a second power railthat are disposed in the first layer on the back side of the integratedcircuit, wherein the first power rail is configured to couple a thirdactive region included in the first transistor to a first supplyvoltage, and the second power rail is configured to couple a fourthactive region included in the second transistor to the first supplyvoltage, wherein the second conductive line is interposed between thefirst power rail and the second power rail.
 14. The integrated circuitof claim 13, further comprising: a plurality of the flip flop circuitsin a plurality of flip flop cells, wherein the plurality of the flipflop cells abut each other along a direction; and a third power rail anda fourth power rail that are disposed in the second layer on the backside of the integrated circuit and pass through the plurality of theflip flop cells in the direction, wherein the third power rail and thefourth power rail are configured to couple, respectively, the firstpower rail and the second power rail to the first supply voltage. 15.The integrated circuit of claim 11, wherein the third conductive lineextends across the first cell to the second cell.
 16. The integratedcircuit of claim 11, further comprising: a third transistor in the firstcell, comprising: a third gate configured to receive the first clocksignal through a sixth conductive line which is disposed in the firstlayer on the back side of the integrated circuit and coupled to thethird conductive line.
 17. A method, comprising: forming an activedevice operating as a scan flip flop circuit on a front side of anintegrated circuit; forming a plurality of first conductive linesextending in a first direction in a first layer on a back side of theintegrated circuit to transmit a first clock signal and a second clocksignal to the active device; forming a plurality of second conductivelines in the first layer on the back side of the integrated circuit totransmit a first supply voltage and a second supply voltage to theactive device, wherein the plurality of first conductive lines areinterposed between the plurality of second conductive lines; forming aplurality of third conductive lines extending in a second directiondifferent from the first direction in a second layer on the back side ofthe integrated circuit to transmit the first clock signal and the secondclock signal between the plurality of first conductive lines, whereinthe first layer is disposed between the second layer and the front sideof the integrated circuit; and forming a plurality of fourth conductivelines extending parallel to the plurality of third conductive lines inthe second layer on the back side of the integrated circuit to transmitthe first supply voltage and the second supply voltage to the pluralityof second conductive lines, wherein the plurality of third conductivelines are interposed between the plurality of fourth conductive lines.18. The method of claim 17, wherein at least one of the plurality ofsecond conductive lines includes a first portion extending in the firstdirection and a second portion extending in the second direction. 19.The method of claim 17, further comprising: forming a plurality of fifthconductive lines extending in the first direction and a plurality ofsixth conductive lines extending in the second direction in a thirdlayer and a fourth layer, respectively, on the back side of theintegrated circuit to transmit the first supply voltage and the secondsupply voltage to the plurality of fourth conductive lines.
 20. Themethod of claim 19, wherein the third layer is sandwiched between thesecond layer and the fourth layer.